Field of the Invention
The present invention relates to pneumatic tires. Specifically, the present invention relates to run flat tires including load support layers.
Description of the Related Art
In a run flat tire including load support layers inside sidewalls, if the internal pressure is reduced due to puncture, a load is supported by the support layers. The run flat tire allows for running for some distance even in the punctured state. Running in the punctured state is referred to as run-flat running. If run-flat running is continued, deformation and restoration of the support layers are repeated. Due to the repetition, heat is generated in the support layers, and the temperature of the tire reaches a high temperature. Tires are desired which withstand the deformation and the high temperature and allow for run-flat running for a long period of time. Tires having excellent run-flat durability are desired.
The run-flat durability can be improved by increasing the thickness of each load support layer. However, the load support layers having a large thickness increase the vertical stiffness constant of the tire. The high vertical stiffness constant impairs ride comfort during normal running. In addition, the load support layers having a large thickness increase the weight of the tire. This increases the rolling resistance. There is also a high demand for run flat tires that have excellent ride comfort and whose increase in weight is suppressed.
Examination regarding a run flat tire is disclosed in JP2010-163108. In this tire, by adjusting the thickness of each side reinforcing rubber (load support layer), improvement of ride comfort and reduction of the weight thereof are achieved without impairing run-flat durability.
Run flat tires are desired which have further improved run-flat durability while deterioration of ride comfort and an increase in the weight thereof are suppressed.
An object of the present invention is to provide a pneumatic tire having improved run-flat durability while favorable ride comfort during normal running and an appropriate weight thereof are maintained.